a wider tire with a lower pressure will provide more flotation due to the fewer pounds per square inch contacting the surface. traction is a combination of things including tread, etc. all other things being equal increasing your contact patch will give you less traction, however all things are not always equal including turning and leaning, meanine a lower pressure tire with tread can provide better traction on wet slick surfaces than a narrow high pressure slick doing the same lean. especially over painted roadway markings

my concern with riding in the rain is a much increased stopping distance if I can stop at all, and hidden potholes under smooth looking puddles, which can wreck a nice new wheel